Dental impression materials are well known in the art and have been applied for a long time. Such materials typically possess a variety of properties including a quick setting behavior, good dimensional stability and sufficient storage stability. Generally, the materials are provided in two components to be mixed prior to use and cure by a crosslinking-reaction.
One widely used class of impression materials is based on addition- or condensation crosslinking-reactions of polyorganosiloxane containing components.
Dental impression materials containing polyorganosiloxane components are typically hydrophobic in nature. In order to make these materials more hydrophilic, the incorporation of surfactants has been proposed. Measuring the contact angle of a water drop on the surface of the mixed composition is an appropriate method to find out to which extent the composition has a hydrophilic or hydrophobic behavior.
U.S. Pat. No. 4,657,959 relates to hydrophilic silicones and contains examples of compositions containing amphoteric and ionic surfactants. With regard to non-ionic fluor-containing surfactants, perfluorinated groups are attached to a polyether moiety via a polyvalent hydrocarbonyl linking group (e.g. —C2H4— or —SO2NR— group).
GB 2,337,524 mentions a silicone composition for oral mucosa impression. The composition i.a. comprises an organopolysiloxane having at least two aliphatic unsaturated hydrocarbons in one molecule and a certain amount of one or two or more non-ionic surfactants.
WO 2007/080071 A2 describes addition-cured dental impression materials based mainly on silicones which provided hydrophilicity in the non-cured pasty state. By application of mixtures of fluorinated surfactants and silicone surfactants water contact angles of the pasty material below 10° were obtained 40 s (seconds) after mixing of the base and catalyst paste and 3 s after setting of the drop on the surface. The non-ionic fluorinated surfactants described contain at least one partly or per-fluorinated hydrocarbon rest, which is connected via an oxygen atom, an amino or a keto group, carboxylic ester group, a phosphoric acid ester and/or amide with an (poly)alkylenoxide radical, an carbohydrate radical, an aliphatic polyhydroxy radical or a nitrogen-containing heterocyclic compound or is at least a per- or partly fluorinated rest which comprise at least one amino-oxide rest.
The fluorinated surfactants taught in WO 2007/080071 A2, however, may not be very suitable for use in dental applications. It was found that generally the surfactants disclosed in this reference may have an adverse impact on other desirable properties of the dental composition. E.g. the fluorinated surfactants described in this reference may cause difficulties during the production process of the dental impression material, e.g. during a de-gassing step needed for producing high quality and gas free compositions.